Intravenous drug use and HIV infections are two linked global health crises since needle sharing is a well recognized mode of HTV transmission. While HIV infection is the leading cause of death among Americans 25- 44 yearsold, injection drug use now accounts for about one-third of all new US AIDS cases reported each year. Cocaine, often abused by HIV-infected patients, has been suggested to worsen the HIV-associated dementia (HAD) via unknown mechanisms. The brain is a target organ for both, the recreational drugs and HIV-1. HAD is an important complication of viral infection and a cause of significant morbidity, and mortality. The underlyingfeature of HAD revolves around two processes: a) productive replication of the virus in macrophages in the brain, leading to encephalitis, and b) neuronal degeneration resulting from the action of secreted byproducts released from infected macrophages, leading to dementia. Cocaine IVDUs are known to have higher rates of HIV-encephalitis, microglial proliferation and clinical HIV dementia. The use of cocaine therefore exacerbates factors that promote HIV replication in the brain. Our preliminary studies demonstrated that cocaine enhanced production of both, the virus and of the virus-promoting cytokine, IL-10 in monocyte-derived macrophages (MDMs). Cocaine also synergized with viral glycoprotein, gp!20, to induce the expression of the neurotoxin, CXCL10 in human neuronal cultures. Based on these findings, we hypothesize that cocaine accelerates the progression of HIV-E by two mechanisms: 1) Cocaine-mediated induction of IL-10 enhances virus-replication in the brain, and 2) synergistic induction of CXCL10 by cocaine & gp!20 accelerates neuronal dysfunction/death. In this application we will test the hypotheses in 3 specific aims: 1) Examine the role of IL-10 in cocaine-mediated up-regulation of SHIV/HIV-1 replication in macaque/human MDM cultures, 2) To determine the mechanism(s) of cocaine & virus protein induced-CXCLlO on neuronal dysfunction/death in vitro. 3) In vivo abrogation of cocaine and gp!20-mediated neuronal apoptosis using antisense CXCL10 DNA therapy in murine models of HTV-dementia. Relevance: This proposal aims to: a) Explore the role of cocaine in accelerating the development of HFVDementia and b) Develop therapeutic intervention strategies for the treament of HAD in cocaine-absuers